1. Field of the Invention
The present invention generally relates to communication format control methods and apparatuses, and more particularly to a communication format control method and apparatus for a mobile communication system which is capable of providing simplex and duplex communication services to a mobile station in each zone via a plurality of base stations.
In simplex communication, a person cannot speak while the other person is speaking. However, the communication between the two persons can be made via a single communication channel (traffic channel TCH1up or TCH1down), thereby making it possible to effectively utilize the communication channel (frequency). For this reason, the simplex communication is popularly used in mobile communication systems including independent systems.
2. Description of the Related Art
FIGS. 1 through 7B are diagrams for explaining the prior art, and show various communication phases and the like conforming to a mobile communication standard of Japan.
FIG. 1 is a diagram showing a communication phase of a duplex communication conforming to the standard. In FIG. 1, MS1 and MS2 denote mobile stations, BS denotes a base station, CAC denotes a common access channel, and USC denotes a user specific channel. The common access channel CAC includes a broadcast control channel BCCH, a paging channel PCH, a signaling control channel SCCH, and a user packet channel UPCH.
When the mobile station MS1 calls the mobile station MS2 by a xe2x80x9cduplex call setupxe2x80x9d, the base station BS in response to this xe2x80x9cduplex call setupxe2x80x9d returns a xe2x80x9ccall setup acceptxe2x80x9d to the mobile station MS1 and pages the mobile station MS2 by a xe2x80x9cduplex communicationxe2x80x9d.
FIG. 2 is a diagram showing a format of a call setup message conforming to the standard. As shown in FIG. 2, the format includes xe2x80x9ctransfer capacityxe2x80x9d in the fourth column. FIG. 3A is a diagram showing a format of the xe2x80x9ctransfer capacityxe2x80x9d in conformance with the standard. A xe2x80x9ccommunication formatxe2x80x9d column is located at an octet 4a shown in FIG. 3A. FIG. 3B is a diagram showing a bit coding of the xe2x80x9ccommunication formatxe2x80x9d in conformance with the standard. In FIG. 3B, xe2x80x9c000xe2x80x9d indicates simplex communication, and xe2x80x9c010xe2x80x9d indicates duplex communication.
Returning now to the description of FIG. 2, when the mobile station MS2 returns a xe2x80x9ccommunication enablexe2x80x9d, the base station BS in response to this xe2x80x9ccommunication enablexe2x80x9d sends a synchronizing signal SB1 to the mobile station MS1 by the user specific channel USC, and specifies a radio channel by the common access channel CAC. In response to this specifying of the radio channel, the mobile station MS1 switches the frequency to the specified radio channel, and establishes synchronization with the base station BS by exchanging subsequent synchronizing signals SB1 through SB4. In addition, the base station BS also establishes synchronization with the mobile station MS2 in a similar manner, and calls the mobile station MS2. When a response is received from the mobile station MS2, a duplex communication state is reached between the mobile stations MS1 and MS2.
FIG. 4 is a diagram showing a communication phase of a simplex communication conforming to the standard. When the mobile station MS1 calls the mobile station MS2 by a xe2x80x9csimplex call setupxe2x80x9d, the base station BS in response to this xe2x80x9csimplex call setupxe2x80x9d returns a xe2x80x9ccall setup acceptxe2x80x9d to the mobile station MS1 and pages the mobile station MS2 by a xe2x80x9csimplex communicationxe2x80x9d. When the mobile station MS2 returns a xe2x80x9ccommunication enablexe2x80x9d, the base station BS in response to this xe2x80x9ccommunication enablexe2x80x9d sends a synchronizing signal SB1 to the mobile stations MS1 and MS2 for a predetermined time by the user specific channel USC, and specifies a radio channel with respect to the mobile stations MS1 and MS2 by the common access channel CAC. In response to this specifying of the radio channel, the mobile stations MS1 and MS2 switch the frequency to the specified radio channel, and when a traffic channel TCH (B/I=I) is received from the base station BS, the mobile stations MS1 and MS2 assume an enabled state accessible by the simplex communication. Here, B/I denotes busy/idle bits.
In this state, when a press-to-talk of the mobile station MS1 is turned ON, the mobile station MS1 establishes a send synchronization between the mobile station MS1 and the base station BS, and thus, the traffic channel TCH (speech) from the mobile station MS1 is received by the mobile station MS2. When the press-to-talk of the mobile station MS1 is turned OFF, the mobile station MS1 releases the right to send, and the mobile stations MS1 and MS2 again assume the enabled state accessible by the simplex communication. The operation of the mobile station MS2 when the press-to-talk is turned ON is the same as in the case of the mobile station MS1.
FIGS. 5 and 6 are diagrams showing a communicating channel switching phase (re-calling type) of the simplex communication conforming to the standard. FIG. 5 shows a case where the mobile station MS1 which is communicating with the mobile station MS2 via a base station BS1 by a simplex communication moves to another zone during the communication. When the down-level deteriorates, the mobile station MS1 searches for a perch channel, and makes a re-calling during communication by a xe2x80x9csimplex communication re-call setupxe2x80x9d with respect to a selected base station BS2. Responsive to this xe2x80x9csimplex communication re-call setupxe2x80x9d, the base station BS2 returns a xe2x80x9cre-call setup acceptxe2x80x9d to the mobile station MS1 by the common access channel CAC, sends a synchronizing signal SB1 to the mobile station MS1 by the user specific channel USC, and specifies a radio channel by the common access channel CAC. In response to this specifying of the radio channel, the mobile station MS1 switches the frequency to the specified radio channel, and establishes synchronization with the base station BS2 by exchanging subsequent synchronizing signals SB1 through SB4. When a traffic channel TCH (B/I=B) is received from the base station BS2, the traffic channel TCH (speech) from the mobile station MS1 is continuously received by the mobile station MS2 via the base stations BS2 and BS1.
FIG. 6 is a diagram showing a case where the mobile station MS1 is making a reception. When the down-level deteriorates, the mobile station MS1 searches for a perch channel, and makes a re-calling during reception by a xe2x80x9csimplex communication re-call setupxe2x80x9d with respect to the selected base station BS2. Responsive to this xe2x80x9csimplex communication re-call setupxe2x80x9d, the base station BS2 returns a xe2x80x9cre-call setup acceptxe2x80x9d to the mobile station MS1 by the common access channel CAC, sends a synchronizing signal SB1 to the mobile station MS1 for a predetermined time by the user specific channel USC, and specifies a radio channel by the common access channel CAC. In response to this specifying of the radio channel, the mobile station MS1 switches the frequency to the specified radio channel, and establishes synchronization with the base station BS1. The traffic channel TCH (speech) from the mobile station MS2 is continuously received by the mobile station MS1 via the base stations BS1 and BS2.
FIGS. 7A and 7B are diagrams for explaining a conventional communication format control method.
FIG. 7A shows a case where a mobile station MS1 in a zone Z1 calls a mobile station MS2 in the same zone Z1 by a simplex communication. In this case, a base station BS1 (that is, a radio line control unit MCU 30) allocates a traffic channel TCH1, for example, with respect to the mobile stations MS1 and MS2 via the common access channel CAC. In this state, when the press-to-talk of the mobile station MS1 is turned ON, the mobile station MS1 establishes a send synchronization with the base station BS1 by the traffic channel TCH1up, and the communication (speech) from the mobile station MS1 is consequently received by the mobile station MS2 via the traffic channel TCH1up, the base station BS1 and the traffic channel TCH1down. When the press-to-talk of the mobile station MS1 is turned OFF, the traffic channel TCH1up is released. Next, when the press-to-talk of the mobile station MS2 is turned ON, the mobile station MS2 establishes a send synchronization with the base station BS1 by the traffic channel TCH1up, and the communication (speech) from the mobile station MS2 is consequently received by the mobile station MS1 via the traffic channel TCH1up, the base station BS1 and the traffic channel TCH1down. When the press-to-talk of the mobile station MS2 is turned OFF, the traffic channel TCH1up is released. Accordingly, although one person cannot speak while the other person is speaking, the simplex communication can be made by use of a single communication channel (traffic channel TCH1up or TCH1down), thereby making it possible to effectively utilize the communication channel (frequency). For this reason, the simplex communication is popularly used in mobile communication systems including independent systems.
FIG. 7B shows a case where the mobile station MS1 in the zone Z1 calls the mobile station MS2 in a different zone Z2 by a simplex communication. In this case, the base station BS1 allocates a traffic channel TCH1 to the mobile station MS1 by the common access channel CAC, and the base station BS2 allocates a traffic channel TCH2 to the mobile station MS2 by the common access channel CAC. In this state, when the press-to-talk of the mobile station MS1 is turned ON, the mobile station MS1 establishes a send synchronization with the base station BS1 by the traffic channel TCH1up, and the communication (speech) from the mobile station MS1 is received by the mobile station MS2 via the traffic channel TCH1up, the base station BS1, the MCU 30, the base station BS2 and the traffic channel TCH2down. However, there was a problem in that the traffic channel TCH1down of the base station BS1 and the traffic channel TCH2up of the base station BS2 are not used in this state.
In addition, when the press-to-talk of the mobile station MS2 is turned ON, the mobile station MS2 establishes a send synchronization wit the base station BS2 by the traffic channel TCH2up. Hence, the communication (speech) from the mobile station MS2 is received by the mobile station MS1 via the traffic channel TCH2up, the base station BS2, the MCU 30, the base station BS1, and the traffic channel TCH1down. However, there was a problem in that the traffic channel TCH2down of the base station BS2 and the traffic channel TCH1up of the base station BS1 are not used in this state.
The above described problems similarly occur when the mobile station MS2 or MS1 which is call-connected by the simplex communication moves from the zone Z1 to the zone Z2 in FIG. 7A during the communication.
Accordingly, it is a general object of the present invention to provide a novel and useful communication format control method and apparatus, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide a communication format control method and apparatus which can improve the simplex communication service.
Still another object of the present invention is to provide a communication format control method for a mobile communication system which is capable of providing a communication service to a mobile station in each zone via a plurality of base stations by a simplex or duplex communication format, comprising the steps of call-connecting a calling mobile station which calls by a simplex communication request and a called mobile station by a duplex communication format, when the calling mobile station is located in a zone different from a zone in which the called mobile station is located. According to the communication format control method of the present invention, it is possible to effectively utilize the communication channels which were not utilized conventionally. For example, in the case of the communication from the calling mobile station and the called mobile station, traffic channels TCH1down and TCH2up are effectively utilized by the present invention. In addition, the mobile stations in this case can communicate by the duplex communication, thereby making it possible to greatly improve the communication service which is originally limited to the simplex communication.
A further object of the present invention is to provide a communication format control apparatus for a mobile communication system which is capable of providing a communication service to a mobile station in each zone via a plurality of base stations by a simplex or duplex communication format, comprising a position registration table which records a zone in which each mobile station is located, a call state management table which manages a present communication format and a request mode of the communication format at a time when calling or called, for each mobile station, and a communication format controller which instructs the communication format of each mobile station by referring to each of the position registration table and the call state management table when a mobile station calls or is called or, when the mobile station moves from one zone to another zone during communication, where the communication format controller instructs the duplex communication format if a request mode when the mobile station calls or is called is the simplex communication and two mobile stations in communication are located within mutually different zones. According to the communication format control apparatus of the present invention, it is also possible to effectively utilize the communication channels which were not utilized conventionally.
Another object of the present invention is to provide a mobile station unit for in a mobile communication system which is capable of providing a communication service to a mobile station in each zone via a plurality of base stations by a simplex or duplex communication format, comprising a communication controller which is operable in the simplex and duplex communication formats, a display unit which displays the communication format of an operating mobile station to which the display unit belongs, and a signal sound generator which generates a signal sound to indicate a change of communication format when the communication format changes during communication. According to the mobile station unit of the present invention, the user can appropriately make the intended communication depending on the control of the communication format on the network side.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.